Hydrogen generation systems exist on the same balance. When the input electricity is expensive, you want to build them to be more efficient, and that costs money, in catalysts and low-loss reaction chambers and such. If a huge amount of energy at peak times is free, then the optimal point is very different, and indeed if you try to minimize capital costs you end up needing something barely more sophisticated than a kettle. Kettles aren't particularly expensive to run!

While competition will quickly drive this towards a more even balance, as cheap storage displaces yet-more excess solar buildout, the point of the argument was just to show why naïvely extrapolating to extreme overproduction (>2x) is misleading.